A telecentric lens is a compound lens which has its entrance or exit pupil at infinity. In other words, the chief rays, that is, oblique rays which pass through the center of the aperture stop, are parallel to the optical axis in front of or behind the system, respectively. An entrance pupil at infinity makes the lens object-space telecentric. Such lenses are used in machine vision systems because image magnification is independent of the object's distance or position in the field of view, referred to as an orthographic view. An exit pupil at infinity makes the lens image-space telecentric.